


Achilles Heel

by NihilismPastry



Series: Requests from Tumblr [6]
Category: Undertale (Video Game)
Genre: BDSM, Body Worship, Bondage, Breeding Kink, Chubby Reader, Dirty Talk, Ecto-Tongue, Ecto-dick, F/M, Female Reader, Mafiatale-AU, Master/Servant, One-Sided Attraction, Soul mate bond, Voice Kink
Language: English
Status: Completed
Published: 2016-10-14
Updated: 2016-10-20
Packaged: 2018-08-21 19:33:00
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings, Rape/Non-Con
Chapters: 2
Words: 5,234
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8257876
Author URL: https://archiveofourown.org/users/NihilismPastry/pseuds/NihilismPastry
Summary: Honestly, she shouldn't have that much power over him.





	1. Chapter 1

**Author's Note:**

> Another tumblr request! 
> 
> Anonymous: The request I wanted to make, before I had chickened out and went with asking a question, was for a onesided gaster x chubby reader. ...How about bondage, body worship/praise, voice kink, and blindflding? 
> 
> AU: Mafiatale

Not many people would guess your...'occupation' after a single glance. You didn't wear the frills and jewels of the other women, and you didn't have the typical model body type. No, you were a normal looking girl that tended to buy cheap clothes, and only wore perfume when your husband 'came home' so to speak. Every Saturday W.D.Gaster would come up your stairs, and invite himself into your home. He'd bring with him that illegal liquor, and would pour him up a glass while you made small talk.

The man would usually answer with short quips, adding nothing of real value to the conversation at first. But then let him get a few glass fulls of his liquor, and suddenly he had plenty to say. Complaints about politics, idle musings about church, and compliments on your hair and dress for the night. It was just his charm, the usual stuff he used when he needed to close a deal with his boss. It wasn't special for you, this act you'd seen a million times before.

Once he had enough liquor, he always took off his hat and set it on the kitchen table. You'd take that as your cue to get up as well and follow him to the guest room. He always made quick work of your clothes, and used another pair of hands conjured of magic to fold them neatly. His actual hands would push at your shoulders, and you'd kneel down in front of him. Thick fingers trailed your face, mapping out skin he'd seen a million times before.

"So beautiful." He rasped, his voice low with a hint of a foreign accent. If there was anything about your husband that you did like, it was his voice. You would make him speak to you on a telephone all night if you could. It was a shame he preferred to speak with his hands. "Delicate bones and skin, I could crush you so easily." He added pressure to your temple, the strumming of the vein there accelerating. "Small and fragile, my Princess."

The words were romantic, but then again he always started things off that way. Words that were sweeter than the cakes he sent you, and faker than your pastor's congratulations at your wedding.

All of it fake, a show put on for convenience. 

The fingers left your face, and you remained in your position as Gaster staggered to the vanity on the other side of the room. When he came back, he had a faithful of silky scarves just for this occasion. He knelt down in front of you, white eye lights roaming over your face. He didn't speak, or maneuver his fingers to instruct you. He just stared in an unsettling manner that always left you more annoyed than worried. "Master?"

Without another word the violet scarf was carefully pressed over your eyes, blinding you to the rest of the world. Skeletal fingers made their way through your hair, and tied a knot in the scarf, keeping it in place. As he secured the blindfold, you felt another pair of hands pluck up your wrists, the tell tale caress of soft cloth hinted that he was tying them up with another scarf.

"Bound and blind, relying completely upon me." His voice was low, barely above a whisper. "My lovely, Princess." The cold fingers brushed up your sides, over your arms, until they curled firmly into your hair. Your breathing picked up when you heard the grating sound of his zipper, and the warm earthy smell of his magic. He carefully pushed your body forward, and a light numbness fell over your lips. "Suck."

You obediently opened your mouth, and his cock wedged itself I to your mouth. It wasn't terribly girthy, nor was it all that long. That wasn't to say its average make was a let down, after all, it was about the craftsman not the tools. You sucked his tip carefully, one hand splayed on the wooden floor to keep you balanced, while the other was curled into a fist. You made sure to keep your legs splayed outwards in an open butterfly position, knowing he liked to 'catch a peek'. 

You released his tip with a wet pop, before scooting closer and taking it back in your mouth. You pulled your head lower this time, and let your tongue lazily flick along the underside of his cock. He hummed in approval, and the hand in your hair tightened. A boost of confidence and red hot pleasure coursed through your veins as you sucked on the dick in your mouth. Spit dripped down the sides of your mouth, and obscene noises reverberated through the room. This wasn't the first time you were glad Gaster had sound proofed the room.

You gently relaxed your jaws, and let your teeth slide over the magic appendage. Gaster hissed and yanked your head back, but the dick remained lodged in your mouth. You halted your movements, listening to the gentle rustle of cloth and felt Gaster's dick twitch. "I admire your enthusiasm, but I only asked you to suck not try to bring me to completion, slut."

The cock was released from your mouth, causing more spit to escape and trail down your skin. The fingers in your hair tightened, and you yelped when you were dragged to your feet. He dragged you towards the bed, your feet stumbling stumbling behind him. You yelped when you were suddenly pushed forward, and all sense of balance was snatched from you. On instinct your hands tried to stop the fall, but they only hit air. It was the rest of your body that hit the bed, smothered in scratchy blankets and legs spread out. 

You pressed your hands behind you until they brushed against the silky texture of the sheets, and pushed yourself backwards until your head was properly laying in the blanket. You refused to snap your neck in the name of sex. The money was not worth a neck cast. 

"On your knees, Princess." You obediently shifted onto your knees, a faint warmth creeping along your face in the position. "Good girl." Warm hands caressed your ass. "What would you like, Princess? Tell me how to please you."

 "Your mouth, master." You arched your back, bringing your ass up higher. "Please eat me out."

Sharp fingers spread your lower lips apart, and warm air ghosted along your wet core. Your fingers curled into your palm when you felt something slick and slimy tease the outer edges. His tongue, like his cock, was made of magic. However it had a more gelatinous consistency, and was as slimy as a newborn squid. However the way it could bend and move, you wondered why he bothered making a dick at all.

You gasped when it slipped between your fold, and prodded at your clit. Just enough pressure to set your veins on fire, but not enough speed to really get you going. You garbled out a moan of his title, but he ignored it as he played with your clit. Gentle sawing movements, and the occasional slap was all you received. When cold air brushed against your pussy instead of warm, you gasped and fought the urge to buck your hips.  However your panic was quickly abated when fingers spread you apart, and two fingers sank into your cunt. They were slick and rigged, but held that special zing of magic that made your insides flutter.

A few quick pumps and you felt your stomach tighten. He was ridiculously good at this. You supposed he ought to be, a mob man like him probably spent half his pay on whores before he 'settled down' with you.

The thoughts were forcefully removed when he curled his fingers, brushing up against that particular spot that made you squeal in delight. A low chuckle answered you as he repeated the movement, managing to hit that spot again. You pressed yourself further into the mattress, your insides wound so tight they were just begging to explode. "M-master, may I...?"

"Of course." A finger began to rub harshly at your clit, causing you to cry out. "Cum for me, Princess."

Your muscles clamped down on his fingers, and a call of his name left your lips. Warmth spread through your body, and curled around every nerve as your orgasm was ripped from you. Walls fluttering lightly, you slowly sank into the mattress, ass still in the air, but eyes shut behind the blindfold. 

You had to please him now, and then you could get some well deserved sleep. You spread your legs wider, putting yourself in his favorite position. "Do you still want me, Master?"

Fingers ghosted along your spine and neck, before grappling to your waist. With a sharp yank, your found yourself in a sitting up position. A warm breath teased along your lips, making them crackle and numb from magic, and your nose wrinkle from the bitter smell of whiskey. You shifted your legs, and found that they brushed along a rougher grade of cloth. You guessed you were sitting on Gaster now.

"You're cruel, Princess." His grip tightened, forcing skin to bunch together under his fingers. "But then your race has a knack for it, don't they?" You felt your heart stammer against your ribs when a pair of bony teeth connected to your lips. "Wanting you isn't even the problem. In fact, I have everything to solve the problem except a single elusive variable."

So it was one of those nights then. Occasionally, Gaster drank far too much, and became a prattling fool. You'd learned to let him talk it out, and to remain silent. For now, the session was over, and you could be yourself. Not the cheap excuse of a wife that Gaster used to show the cops he had some sort of alibi. You weren't wanted or needed, regardless what he was saying now, and that was why it hurt so much. Why you could barely stand to look at his face. You pressed the blindfold closer to your eyes, hoping they caught the tears as he continued his drunken whispering.

"I love you, and yet my dearest princess will never love me back."


	2. Take

**Summary for the Chapter:**

> You brought him to his knees, but he was still strong.

**Notes for the Chapter:**

> So the requester asked for a second part. Since I aim to please, here it is! Unlike last time, I won't tell you guys what the direct request was, so it won't ruin the story. ;)

You stared at the small apartment with a smile. It wasn't much, just one room with cobwebs and dust everywhere, but it was home. Well, it would be tomorrow morning. All you had to do was sign the paperwork, and the tiny Parisian apartment was yours. Far away from your old life, but placed in a destination where a new life wouldn't be difficult to forge. After all, what place was so spectacular and amazing as Paris?

You flounced over to one of your boxes and began to unpack. You didn't take much from your old home in Ebbot. Thanks to the circumstances, you couldn't afford to move a lot of your things, and you didn't want to go to your husband for money. "Ex-husband."

You whispered the reminder, your smile faltering. The divorce, if you could call it that, happened a year ago. Surprisingly enough he had easily let you go, even wishing you luck with your new life. You had worked several jobs in order to make some money, and had sold any of the gifts and jewelry that Gaster had given you. Pulled together you had just enough for the boat ticket, first two months of rent, and a little money for emergencies. 

You took out a green towel and set it on the floor, before diving back into the box to retrieve your eating utensils. Even though you had swept and mopped the wooden floors that morning, you still didn't trust them yet. For all you knew, the last person to live there could have been a sewer worker. The thought made your nose wrinkle, and you made a mental note to buy more floor cleaner in the morning.

* * *

Over the next two months, you had managed to start your life. Your home was properly set up, you had found a job at the local butcher's as a store clerk, and even found a friend in your next door neighbor. Yes, it was hard to talk to people sometimes, and you often found yourself missing Ebbot, but you were still...happy.

You pulled your rain coat tighter around your body as you went up the stairs of the apartment building. One thing you missed about America, was the fact that you had lived on the ground floor. You didn't like living on the top floor, every time you aired your laundry, you were afraid of falling out the window and into the busy street below. Maybe you could deal with it if there was a great view, but looking at a dingy brick building wasn't 'quality scenery' in your book.

You fished out your keys and opened up your door, glad to be back on your cosy apartment. You double checked the lock before stripping off your jacket and hung it up to dry. Since it was early evening, you figured you could read for a bit before starting dinner. You went to your small bedroom and unlocked the door, just to find a dozen red roses in a black vase.

Your eyebrows furrowed as you went over to your bedside table, fingers tightening around your keys. This strange display had started a week ago. Gorgeous flowers would wind up in your vase, without any card or label. You had given the small yellow vase to your neighbor, but that had resulted in this new vase being set up. And when you went to remove it...Someone had the audacity to glue the damn thing to your cheap table. 

You yanked up the bundle of long stemmed roses and marched to your window. You flung it open and then tossed the roses into the alley below. With a huff you slammed the window shut, and dropped your keys onto the bedside table, before stripping out of your blouse. Honestly, how were they even getting in? You had even locked your bedroom this time! "I'll have to ask Anette to look after the apartment tomorrow."

Once you were fully undressed, you knelt down and grabbed a book from under the bed. It was one that had a blonde woman leaning against a well muscled man on the cover. Both wore scanty clothes, and were surrounded by blood red roses, and swaths of white satin. It was a book you had borrowed from Anette, and it was a very fun way to practice reading French. Not that you would ever recommend such a book, it was something your mother would set on fire them drag you to a priest if she ever caught wind of it. 

But you adored the 'bodice ripper' stories so much. The romance, the tension, and the lovely world the author had woven. You read those stories in order to escape the harsh world you currently lived in, and give you a taste of love you had never experienced.

Wish fulfillment of the most blatant kind. 

You sighed and leaned back against your blankets and flipped to your current page. A sex scene was starting, so you decided to take care of 'business' while reading. You tucked the book nearly between three fingers, before using your free hand to tease your outer lips. 

"I see you've replaced me then."

You dropped the book and sat up straight, your arms wrapping around yourself to hide your intimate parts. Standing in front of you was none other than your ex-husband. His hands were in his coat pockets, and his gaze was fixated on your abandoned book. 

"H-how?"

He glanced up to you and kicked the book out of his way as he approached the bed. From your place you could smell car exhaust and rain. It was the first time you'd ever had him around and not smell the sharp scent of his alcohol. He took his hands out of his pockets and signed. ' _I have business here, actually. A designer I fund is releasing a new line, and I need to be here for the opening night at his gallery.'_

"And that gave you the right to come into my home?"

_'Naturally.'_

You shook your head, hair mussing up from the force of it. "No, that's not how divorce works. You have to stay away from me-"

 _'Actually, I simply don't have to provide for you,'_ He ignored your attempt to cut him off. _'anything else is left up to me.'_ You backed further away from him as he knelt down and crawled into your bed. When you felt the rough brick wall dig into your back, you felt your blood run cold. A set of warm hands pressed against your face, it was gentle, almost loving. ' _I have waited a year for you to calm down and try to achieve your dreams, Princess. I think I was being most generous, don't you agree?'_

"Generous?" The word was spat out like hot venom. "I _divorced_ you, the fact I didn't rat you out to the police was generous on my part." You smacked his hand away, and pointed to the door. "Now get out, I'm no longer your personal whore."

 _'Is that what you think you were?'_ He shook his head. _'I can assure you, you meant much more to me than a quick lay, Princess._ ' He grabbed your chin and brought you forward again, mouth creaking open, and his voice rasping out. "Let me show you how much I love you."

Your heart rate accelerated, and you tried to jerk your head back to no avail. Thin bone lips connected with your fleshy ones, magic sparking on your lips. Within seconds you felt his tongue, and you brought your jaws down hard. A low growl, and more force behind the kiss was all you earned. Unwillingly your jaws and were pried apart, and his tongue made its way inside. A surge of magic flooded into your mouth, coating your tongue, and slipping into your throat. A choked hiss escaped you, but was ignored as you floundered in the magic. With all the speed of cold honey, your limbs began to slow down, and you felt a heavy weight in your stomach. 

You reached up with a shaking hand, an attempt to pry him off, but your hands merely brushed against his face. Slowly you were falling, falling deep within yourself, deep within the darkness...

Which only became darker...

Yet darker...

* * *

You stared up at the ceiling, fingers curled and glare firmly in place. You were curled up in a satin robe, and nested in a thick velvet colored blanket. Above your head was a colorful painting of flowers on a back drop of a clean cream color. The rest of the strange room was decorated with dark furniture, and the thick curtains were drawn back to show a sky full of stars and darkness. 

You would get hp, maybe see the view, but a pair of skeletal arms were wrapped around your waist. Your body was propped against strong ribs, and there was a firm gaze screwed to the back of your head. "Gaster..."

"Yes, Princess?"

You sighed and twisted yourself around to look at the skeleton. His fingers traveled over your too soft skin, dipping past the robe and trailing up your thigh. "Where am I? What did you do to me?"

"You're in my hotel room." He said, voice almost at a whisper. "I thought it was only appropriate, your home was a hovel, and I refuse to allow you to remain there any longer."

"That's not your choice!"

"No, but I will not allow my mate to live in such disgusting conditions." You gasped and clenched your thighs when your felt cold fingers dive into your core. The rigid bones felt good against your body, and you had to actively remember this was against your will, that your body was merely reacting to the stimulation your clit.

You tried to raise your arms, but the skeleton constricted his own, forcing you to keep them at your side. When you kicked your legs out again, two hands materialized, and pinned them down into the plush bed. "This is for your own good, Princess. You need me in your life. For a submissive mate to be without their dominate is suicide. I understand you felt that your life was not your own, so I let you free. Now that you have had your freedom, you must return to me."

You bit your lip when he parted your robes, removing his arm long enough to open the cloth to the cool air. Your nipples became erect, and goosebumps grew against your skin. Another magic hand was conjured and this one was used to tweak one of your nipples. "I-I'm not something you own. What you're doing now I-it's a crime."

"Ah, but you forget," He used his real hands to twist you around, and for the first time you actually looked at him. There were dark ridges under both eyes, his teeth seemed sharper, and there was a dangerous glow of magic in his sockets. "I commit crimes for a living. So who better than to steal you back, than a mafia boss?"

You weren't given a chance to respond, and his lips were smashed against yours. You tried to scream. But his tongue wormed its way into your mouth, tasting every surface that you had denied him. His fingers raked against your flesh, and they made your skin crawl. Even with all the skill he possessed, it still felt like bugs marching across your skin. 

You didn't want this.

You wanted out. 

You ripped your face away from his, and did the only thing that came to mind: You spat in his face. The clump of saliva dripped down the side of his cheek bone, and fell with a dull splat onto your robe. All movement topped against your body, and for a moment you thought he was done. "Gaster...I don't love you. Not as a husband, or a mate, or even a friend. If you let me go now, I promise not to tell a soul what happened here tonight." 

Violet eye lights stared you down. The magic behind them crackled, and you could almost taste it on your tongue. Then slowly his grip on you tightened, and his magic hands slammed you back into the bed. Your vision blurred for a moment, but when it returned, you saw a single violet flame sputtering in the skeleton's left eyes, the other devoid of anything. It was just a crawling darkness that made you shudder.

He lowered his face down, and you stiffened against him. He did n seem to care as he nuzzled his nasal cavity into your neck. "It's funny. I thought your rejection would hurt more than it does, but I know you don't mean it. If you did, then surely your soul wouldn't call for help." A warm hand pressed against your chest, and with a sharp tug, you felt the wind knocked out of you. Shimmering above you both was a glass like heart, it was smaller than a ring box, and was a lovely pale blue with a black ring around it. "That ring is my own magic," He said. "And your soul is clawing at it, desperate for me."

"Because I want you to stop!"

 A finger brushed against your core again, this time hurrying itself into the almost dry cavern. Gaster didn't seem to care as he rubbed against your sensitive walls, another pair of hands reaching up and clawing at your breasts. The nipples were pinched and rolled against the cold bones. Meanwhile a second pair of hands lifted your hips up, allowing the fingers to prod deeper into your pussy.

 Gaster growled above you, his tongue flicking out of his mouth and laving against your clammy flesh. Every so often he would bite down, hard enough to elicit a frightened gasp from you. He rumbled against your neck and pulled himself away from you entirely. His heated gaze looked you up and down before he took off his coat and tossed it across the room. Next went his tie, and crop white button down. The movements were hurried, his bones grinding and popping from the movements. 

You had never seen him so eager before, and this scared you. You dug your limbs into the sheets and arched your back, trying to break the hold, but a burst of magic forced you down again. Your soul hovered over your exposed body, pulsing with a dim cyan light. Bony fingers reached for the small prize, and you felt nothing. It was said that I'd someone touched your soul, it was all about the intent, but with Gaster you didn't feel anything. 

No sadness.

Lust.

Anger.

Greed.

You felt literal nothing, and it scared you more than anything else you could have felt. Gaster smirked down at you as his pointer finger traced the left crest of your soul. "It's beautiful and healthy. I'm proud to be bonded to such a mate, a strong human soul is a rare commodity."

He used his free hand to flick at the button of his slacks, and slid out of them with ease. He was now completely naked, and it was the first time that you had seen him that way. He had more ribs than the average human, and they were thicker as well. His spine had a large gash in it, but he seemed to move just fine. All together and he was a skeleton, a very insane skeleton through and through.

He muttered something to himself as he cupped a hand to his pelvis. Your mouth went dry as he summoned his dick in a flurry of magic. Your thrashing became harder, but you didn't move an inch as the hands gripping you pushed you further into the mattress. His cock was different now, it was far girthier than it used to be, and seemed to be a deeper shade of purple. He stroked it a few times, a breathy sigh escaping his lips.

"You don't know how many times I've dreamt of this. How long my soul needed this." The hands dragged you into a sitting position, hovering you over his cock. "Your body is so full of my magic now, it's almost romantic."

"I hate you." You choked out. "I hate you so much."

"Hate is merely an emotion fueled by chemicals." He said. "It will be eased away in time."

With that he began pushing himself into your tight cunt. You gasped and tried to haul yourself backwards, but he continued pulling you down. It had been a long time since you felt something so big inside your body. Your walls stung as they stretched to accommodate him, fueling your love for pain and pleasure. You shut your eyes and tried to ignore it. His quiet whispers, your heavy breathing, his steel grip. 

When you were finally full of him, he didn't give you a moment to adjust as he slid you back up again, then slammed you back down. You screamed out, but he slammed his lips to yours in a bruising kiss. He made you ride him hard and fast, his hands bruising your hips and thighs. When breathing became difficult he let you go and kissed down your neck until he got to the juncture of it and your shoulder. He opened his mouth wide and bit down on the tender flesh.

It hurt.

Blood flowed down your skin, and your screams ripped through your throat. For once, he didn't seem to care as he continued to pound into you, his mouth practically sealed to your flesh. Words bubbled out of your mouth, some straight up curses, while others were desperate pleas. It wasn't until you tasted salt that you realized you had begun to cry as well. Above you both, your soul began to pulse faster, mixing with the black and dragging it into its crystalline surface. 

Suddenly you felt something rip out of you, and Gaster was in your line of sight again. His mouth was smeared with blood, and his magic was glowing brighter in his eye. He allowed on of his hands to release your arm, and trailed down over your skin and to your clit. Two fingers began rubbing hard and fast, making your insides flood with warmth. 

He pressed a hand to your back, forcing you to come closer to him. Your breasts raked against his bones, stimulating them further, and making you sick. 

"Cum for me, Princess." The raspy command made your stomach clench further, and you shook your head wildly. A low growl rumbled from the Skelton, and you were slammed onto your back. Your robe chafed against your skin, and the sharp edges of bone cut into your bruises. The skeleton continued his furious rutting, sockets narrowed. "I don't have to make this pleasurable for you, I merely choose to do so." As if to punctuate his point, he slowed down, but made his thrusts deeper, managing to glide against every nerve inside your cunt. You hissed, but could do nothing with the solid weight on top of you. He increased the pace of the finger rubbing your clit. "Cum."

Against your will, your walls squeezed around his cock, earning a deep growl of approval. Pleasure rocked your body, and made your nerves spark as you ride out your orgasm. When it was finally only soft bursts of warmth in your bones, you flared up at the skeleton, but he didn't seem to care as he continued to fuck you. His pace was becoming sloppy, and his strange mutterings were becoming louder. 

"Do you feel that?" He said, his voice almost guttural and static. "My magic building up inside you? My soul is gathering itself and a new life for you." He leaned down and moaned, his spine arching with a particularly deep thrust. "My soul will breed you, Princess. It's going to create a child formed of magic and trapped within a physical form. **Our child**."

Adrenaline began to pick at your mind again, and you bunched your muscles, desperate to flail against him. He chuckled, and a hand wrapped around your throat, cutting off your air supply. The red alarms in your head blared, and anxiety ate at your insides. Slowly the world around you began to darken, and all you could focus on was the savage thrusts in your cunt, and the buzzing in your head. 

Then suddenly you felt something warm burst inside you. It was light and airy, yet filled with something that clung to your walls. Gaster pumped himself a few more times, filling you to the brim with his magic. You opened and closed your mouth, but Gaster kept a firm hand on your throat. "Just a moment longer. The precipice of death makes you fertile, Princess." He carefully dragged you up, and held you close, the hand still tight around your throat. Behind him you could see the murky glow of your soul, plagued with enough black to make it look like it was rotting. "Just a moment longer and you both will be mine."

 

**Notes for the Chapter:**

> So...? That was a thing. In case you were wondering, Reader didn't consent to any of this, and she didn't enjoy it at all. So it's straight up rape, even if she is his soulmate.

**Author's Note:**

> Poor Gaster, his love was not realized. And the only reason he's waxing poetic, was due to being drunk. I should write a version of him being sober and it'll go like this.
> 
> 'They fucked, he left then got very drunk. The End'
> 
> You know what doesn't get drunk, my tumblr. http://nihilismpastry.tumblr.com


End file.
